We will study the structure and function of the chicken oviduct progesterone receptor. The DNA-binding A subunit of this protein will be tested for its interaction with cloned fragments of the chicken ovalbumin and ovomucoid gene. Subunit-subunit assembly of the intact protein will be studied by reconstitution of partially-purified receptor A and B proteins to determine the stoichiometry of the complex. Structural studies of the purified proteins will include amino acid sequencing of the hormone-binding domain, isolation of proteolytic fragments containing the DNA-binding site, and immunologic characterization using monoclonal antibodies to receptors. The hormone-binding region will be studied using covalent attachment of labeled steroid to the proteins by photoaffinity attachment. Finally, cell-free specific gene transcription studies will be undertaken using purified intact receptor plus or minus hormone in combination with probes for ovalbumin gene transcripts in vitro.